New methodologies are proposed for the detection and quantitization of very small amounts of proteins and DNA sequences. A new gold particle will be used to label target biomolecules, then stained with metallic silver by exposure to aqueous silver (I) ions and a reducing agent. The silver will then be extracted and determined in aqueous solution, using dye coupling reactions at a polymer surface in conjunction with spectrophotometric measurements. Colormetric analysis, catalytic spectrophotometric measurements and anodic stripping voltammetry will also be used to develop fast, simple amplification procedures for the silver-stained gold label. Calculations indicate that sensitivities over 10,000 times greater than those currently available can be achieved: this would allow the detection of 1 x 10 to the -23 mole of antibody or DNA (equivalent to 8 X 10 to the -19 g of alkaline phosphatase, or 1.2 X 10 to the -20 g of a four-base oligonucleotide).